Internal combustion engines and electric motors generate torque, and are therefore used as prime movers in vehicles and other mobile or stationary systems. Engines in particular convert chemical energy of a supply of gasoline or another combustible fuel into mechanical motion. In a typical gasoline engine, a reciprocating piston is connected to a crankshaft via a connecting rod. As an intake valve to a given engine cylinder opens during an intake stroke, the piston moves in such a way as to admit a mixture of air and fuel into the cylinder. The fuel/air mixture is then compressed within the cylinder by movement of the piston. A spark ignites the compressed mixture to drive the piston to a bottom stroke position, at which point a cylinder exhaust valve opens to allow post-combustion exhaust gasses to exit the cylinder. The exhaust gasses are ultimately discharged to the surrounding atmosphere via a tailpipe assembly. Compared to the low levels of sound typically emitted by an electric machine, the combustion process can generate substantial amounts of engine noise.